I'm recording full HD clips with my Sony HDR-SR10. These files have the extension m2ts.

I would like to stitch together a few individual scenes to make a short clip to replace the individual scenes. After creating the new clip I would like to permanently erase the original individual scenes. I'm not planning to do nothing fancy, no titles or anything, the objective is just to stitch the scenes together to have only one multiscene (albeit small) clip.

What format from PE8 should I use to save the stitched clip in order to preserve original quality?

Now, when it comes to export, the choice would be Share/Personal Computer/MPEG, using the preset of

H.264 1920 x 1080i30 (or H.264 1920 x 1080i25)

or

MPEG-2 1920 x 1080i30 (or MPEG-2 1920 x 1080i25)

Often the MPEG-2 1920 x 2080i is selected because it demands less processing power.

Even though you imported video with Dolby Digital 5.1 channel (AC-3), your export audio will be Dolby Digital Stereo (2 channel). See my First Look thread here for more details on 5.1 channel and Premiere Elements 8.

That important focus with the HDV HDV 1080i with frame size 1440 x 1080 (4:3) is that is accompanied by the HD Anamorphic which encodes so that your video 1440 x 1080 (4:3) is stretched on display to give the 16:9.

With AVCHD Full 1080i with its frame size 1920, 1080 (16:9), you are dealing with Pixel Aspect Ratio = square pixel so that you do not have the HD Anamorphic with its associated stretch.

That is my understanding of the situation. If you are working with AVCHD, for export I would explore the merits of Share/Personal Computer/MPEG with MPEG-2 1920 x 1080i as mentioned in an earlier post.

Just a clarification add on which I do not know is necessary, but I will add it anyway

With either 1440 x 1080 with the HD Anamorphic or 1920 x 1080 with square pixel, the end result is the same 1920 x 1080. In the case of 1440 x 1080 with the HD Anamorphic, the HD Anamorphic results in the stretching of the 1440 x 1080 to 1920 x 1080 display possibility.